Photographic flashlamp unit

ABSTRACT

A flashcube in which the reflectors are of a thermoplastic material which will become distorted in the area around the lamp by the heat from flashing to thereby provide ready recognition of a used lamp.

United States Patent Donald W. Hartman Warrensville, Pa.

June 1, 1967 Nov. 9, 197 l GTE Sylvania Incorporated Inventor Appl. No. Filed Patented Assignee PI-IOTOGRAPl-IIC FLASI-ILAMP UNIT 3 Claims, 3 Drawing Figs.

US. Cl 240/1.3, 116/114 V, 240/103 Int. Cl G03b 15/02 Field of Search 240/ 1 .3

I? llllln JIM? [56] References Cited UNITED STATES PATENTS 3,327,105 6/1967 Kottler et al 240/1.3 3,392,273 7/1968 Fink et a1 240/l.3 3,223,526 12/1965 Grieshaber et al 264/230 X Primary Examiner-Samuel S. Matthews Assistant Examiner--Fred L. Braun Attorneys-Norman .l. OMalley and Joseph C. Ryan ABSTRACT: A flashcube in which the reflectors are of a thermoplastic material which will become distorted in the area around the lamp by the heat from flashing to thereby provide ready recognition of a used lamp.

PATENTEUuuv 9 Ian 3, 6 l 9 .5 89

DONALD W. HARTMAN INVENTOR ATTORNEY PI-IOTOGRAPHIC FLASIILAMP UNIT This invention relates to photographic flashlamp units and more particularly to those in which each lamp is provided with its own individual reflector, such as flashcubes for example.

As presently manufactured, the flashcube consists of four subminiature high pressure lamps mounted on a molded polystyrene base having camera attachment means and lamp contacts depending from the bottom surface. Each of the four lamps is provided with individual semiparabolic, specular reflectors with both lamps and reflectors enclosed in a transparent, molded, polystyrene cover which is ultrasonically welded to the base. The vacuum-aluminized reflectors are formed from cellulose propionate.

After flashing flashcubes of current design, the most obvious visual indication of use is a change in the appearance of the lamp. In most flashlamps, particularly high pressure, subminiature, zirconium type lamps, the heat from combustion causes the transparent, exterior cellulose acetate lacquer coating to bubble and become whitish or translucent in appearance due to the light-scattering effect of the small bubbles formed in the lacquer and the white zirconium oxide deposited on the interior glass wall of the bulb. There is a very little distortion or change in the specular appearance of the reflector after lamp flashing, and those changes that do occur are almost completely masked by the lamp. The only other visual indication of use is the disappearance of the zirconium shreds.

Prior to the use of the flashcube, flashlamps were usually used with relatively large reflectors, and the nonautomatic operation of these flashguns usually requires that the used lamp be discarded after flashing. The use of flashlamps with nonautomatic flashguns presents virtually no problems to the photographer with respect to distinguishing flashed from unflashed lamps, since normally, flashed lamps are not retained. The operation of the flashcube frequently requires the photographer to carry at least one cube with one, two or three flashed lamps along with the remaining unused lamp or lamps. In use with the automatic operation provided with many cameras, a used lamp in a flashcube can be rotated into the flashing position, or a partially used cube can be attached to the flash socket so that a used lamp is positioned for use. The recognition of a used lamp in a flashcube, at a quick glance, is hindered by the small size of the flashlamp-reflector unit and the brilliant specular appearance of the reflectors. Also, the flashcube is commonly viewed as a complete unit, as opposed to the case where a lamp is positioned in a relatively larger reflector, thereby making the distinction between lamp and reflector more apparent to the photographer.

In view of the foregoing, a principal object of this invention is the provision of some readily recognizable, reliable indicator which will quickly and accurately inform the photographer that a lamp has in fact been used.

I have found that reflectors formed from biaxially oriented polystyrene and rigid polyvinyl chloride, both copolymer and homopolymer types, are distorted in the area around the lamp by the heat from flashing. This distortion destroys the specular appearance of the aluminum surface coating, producing a matte, satin type of surface, 5 well as wrinkling and gross distortion of the reflector contour. In the case of biaxially oriented polystyrene, the distortion is even more severe, since the plastic closest to the lamp melts and shrinks away from the lamp. However, the distortion in polystyrene reflectors tends to be more localized about the lamp than for the the polyvinyl chloride reflectors, because of its higher heat distortion temperature.

The amount of distortion produced in polyvinyl chloride reflectors by the heat of a flashing lamp can be controlled by adjusting the reflector-forming temperature coupled with sufflcient pressure to form the reflector completely. Polyvinyl chloride, and its copolymers formed at temperatures to 50 F. lower than normal for thennoforrning results in reflectors which show considerable distortion (30 to 70 percent of the visible curved reflector surface), while reflectors formed at maximum forming temperatures have practically no visible distortion when heated by a flashing lamp. Reflector distortion results primarily from from conduction and convection heating effects rather than from absorbed radiant energy, because of the highly reflective aluminum coating which is between the plastic reflector and the flashing lamp. Hence, there is no significant loss in the photometric efficiency of the reflectored lamp due to the time factor.

Biaxially oriental polystyrene and rigid, nonplasticized polyvinyl chloride and its copolymers offer further advantages of low material and reflector fabrication costs because of the increased speed with which they can be vacuum aluminized. Vacuum-pumping speeds for polystyrene and polyvinyl chloride can be twice as fast as for normal plasticized cellulose propionate.

Although the foregoing specific materials are particularly desirable for the reasons noted, it will be readily apparent to those skilled in the art that other thermoplastic materials having sufficient residual stresses to produce substantial, readily visible distortion when heated by a flashed lamp will provide a satisfactory flashed lamp indicator.

IN THE ACCOMPANYING DRAWING FIG. I is a front-elevational view of a flashcube showing an unflashed lamp in a cellulose propionate reflector.

FIG. 2 is a front-elevational view of a flashcube showing a flashed lamp in a cellulose propionate reflector.

FIG. 3 is a front-elevational view of a flashcube showing a flashed lamp in a biaxially oriented polystyrene reflector.

The flashcube of FIG. 1 comprises a substantially square base 2 on which four photoflash lamps 4 are mounted, one along each side thereof, four reflectors 6, one being disposed behind each of the lamps 4, and a transparent cover 8 enclosing the lamp-reflector assemblage and secured to the base 2. Each lamp 4 comprises a hermetically sealed tubular glass envelope 10 containing an ignition system including lead-in wires 12, a combustible such as filamentary zirconium l4 and a filling of a combustion-supporting gas such as oxygen at a pressure of at least several atmospheres. The lamp envelope I0 is provided on the exterior thereof with a transparent, cellulose acetate lacquer protective coating I6. The base 2 is provided with a plurality of apertures therein, through which lead-in wires I2 from each lamp 4 extend. The base is further provided, on the underside thereof, with a depending ring 18 over which the lead-in wires are wrapped and a central depending post 20 for mounting the flashcube on a socket provided therefor on a camera or other equipment.

The flashcube of FIG. 2 is the same structurally as the flashcube of FIG. 1 except that the lamp has been flashed. Although the filamentary zirconium has practically disappeared and a substantial portion of the protective coating has bubbled and become whitish or translucent in appearance, it will be noted particularly that there is no visual indication of any change in the reflector 6a of cellulose propionate.

The flashcube of FIG. 3 is the same structurally as the flashcube of FIG. I except that the reflector is of biaxially oriented polystyrene and the lamp, like the lamp in FIG. 2, has been flashed. Although the protective coating 16b in FIG. 3 is in substantially the same condition as the protective coating 16a in FIG. 2 after the lamps have been flashed, it will be noted that there is a significant difference in the appearance of the reflector 6b of biaxially oriented polystyrene in FIG. 3 as compared to the reflector 6a of cellulose propionate in FIG. 2. Portions of the reflector in the area around the lamp have been distorted by the heat from flashing of the lamp. This distortion, as indicated above, destroys the specular appearance of the aluminum surface coating, producing a matte, satin type of surface, as wall as wrinkling, gross distortion of the reflector contour and a melting and shrinking away of the plastic from the lamp. This condition provides a readily recognizable, reliable indicator which will quickly and accurately inform the photographer that the lamp has in fact been used.

What I claim is:

heated by the flashing of its associated lamp, and having a highly reflective coating thereon.

2. The combination of claim 1 in which said thermoplastic material is biaxially oriented polystyrene.

3. The combination of claim 1 in which said thermoplastic material is rigid polyvinyl chloride.

i i i i i 

1. A photographic flashlamp unit comprising: a base member; a plurality of photoflash lamps mounted on said base member; a plurality of reflectors arranged on said base member in operative relationship respectively with said photoflash lamps; and a transparent cover enclosing said lamps and reflectors, each of said reflectors being of a thermoplastic material having sufficient residual stresses to produce substantial, readily visible distortion thereof when heated by the flashing of its associated lamp, and having a highly reflective coating thereon.
 2. The combination of claim 1 in which said thermoplastic material is biaxially oriented polystyrene.
 3. The combination of claim 1 in which said thermoplastic material is rigid polyvinyl chloride. 